The purpose of this article is to challenge conventional thinking about ventilation and create change to make our communities safer and our built environment a better place to work and live. Throughout my 33-year career in the Testing, Adjusting, Balancing, and Commissioning of HVAC systems, there have been several cycles where the industry has been agitated by Indoor Air Quality (IAQ). Some building owners take it more seriously than others because of past experiences in costly modifications to unhealthy buildings. Others have not had that experience and therefore do not take the necessary steps to proactively maintain air quality.
A school district that was recently recognized as Best-in-Class in four categories by the US Department of Energy’s Office of Energy Efficiency & Renewable Energy learned this lesson in 1999. That year, this school district spent $7.7 million dollars to “gut and rebuild” an elementary school due to IAQ problems.
In short, the lesson learned from this costly repair is that the “V” in HVAC (Ventilation) is an important driver of occupant satisfaction and it is better to be proactive when designing, installing, testing, adjusting, balancing, and commissioning the HVAC systems than it is to take a wait-and-see approach. This school district is to be applauded for their initiative-taking approach to efficient and healthy buildings.
The district hired a former National Environmental Balancing Bureau (NEBB) certified Testing Adjusting and Balancing professional to work on staff as the Director of Energy Management. The district recognized the importance of controlling its energy costs (via a NEBB certified professional), but not at the expense of IAQ. The district mentions in its Best-In-Class citation:
“A TAB Professional is utilized by the school district when installing new HVAC equipment, performing HVAC retrofit, conducting HVAC commissioning or general inspection and maintenance. The district tested HVAC airflow and system capacity, reviewed documentation on HVAC system design values relied on facilities working knowledge of HVAC system, consulted with HVAC contractors, and consulted with filter suppliers to determine the highest MERV filtration possible without adversely affecting HVAC equipment. The HVAC system TAB and commissioning/recommissioning, typically costing 3% of the initial mechanical system costs. Key lessons learned: HVAC digital controls are often initially programmed based on vendors’ previous projects. New systems need testing and verification through trending beyond the warranty period.”
Throughout my career, I have heard may times “You can only expect what you inspect,” “You can only manage what you measure,” and “To assume will make an *** out of you and me”. The value of a certified professional, with hands-on field experience, is important. To aid in this effort, it is vital to understand a few valuable definitions and discussion points to help articulate the value associated with efficient healthy buildings. Some of these will make you go “Wow!” while some will make you question “Why?” And that’s the goal.
Definitions
We hope that these definitions will make you think deeply about ventilation and why we should strive for clean air in buildings and not just acceptable IAQ:
Ventilation
The exchange of air between the lungs and the atmosphere so that oxygen can be exchanged for carbon dioxide in the alveoli (the tiny air sacs in the lungs). This medical definition of ventilation is very clear in stating what ventilation is and why it is important. In its simplest form ventilation is an exchange of air and the atmosphere. The average adult breathes, inhales, and exhales, twelve to sixteen times per minute. Ventilation and respiration are two processes that are involved in supplying oxygen to the body.
The main difference between ventilation and respiration is that ventilation is the provision of fresh air into the lungs while respiration is the gas exchange between the body and the external environment. Respiration rates may increase with fever, illness, and other medical conditions as well as exercise. Therefore, we “off gas” at a greater rate when we are sick, and we need to remove these harmful gases as close to the source as possible and not spread them around the room or building.
The ASHRAE definition of ventilation is: “The process of supplying air to or removing air from a space for the purpose of controlling contaminant levels, humidity, or temperature within the space.” The quality of ventilation will deteriorate over time when one or more of these processes is inadequate, such as dirty filters, improperly installed filters, damaged filters, a reduction of outside air, or the improper distribution of supply, return and/or outside air.
Acceptable Indoor Air Quality (IAQ)
ASHRAE standard 62.1-2019 Ventilation for Acceptable indoor Air Quality – “Air in which there are no known contaminants at harmful concentrations, as determined by cognizant authorities, and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.”
Is this an acceptable definition of the air we want entering our bodies? Would we drink water if only 20% of the people claimed to be dissatisfied with the taste, smell, color, or headaches? During the COVID-19 pandemic people refused to go to work out of fear of getting sick from the air they breathe. How many business, schools, or manufacturing facilities had a 20% infection rate during this period? The EPA estimates that Sick Building Syndrome accounts for $60 billion in lost revenue per year and it’s estimated that $220 billion is lost in worker productivity due to absenteeism and employee sickness.
Breathing Zone
ASHRAE standard 62.1-2019 “the region within an occupied space between planes 3 inches and 72 inches (75 and 1800 mm) above the floor and more than 2 feet (600 mm) from the walls or fixed air-conditioning equipment”. Having clean air in the breathing zone is critical to keeping the human body healthy and productive.
Air Changes (ACH)
Air Changes per Hour is a measurement of how many times a volume of air within a space will be conditioned and filtered before being returned into the space. Theoretically, the air never leaves the space and only gets reconditioned.
Air Exchanges (AXH)
Air Exchanges per Hour is a measurement of how many times a volume of air within a space will be added (outside Air) or removed (Exhaust Air) from the space. Outside air may be delivered to a space as 100% outside air or as a percentage of total air being supplied by the Air Handing Unit.
The United States White House Office of Science and Technology (OSTP) along with the U.S Environmental Protection Agency (EPA) recently launched the “Clean Air in Buildings Challenge.” Ventilation is more than increasing outside air. If the outdoor air is not properly distributed to the breathing zone or the return air path is cross contaminating the breathing zone, then are we accomplishing the ventilation intent? Dr. Alondra Nelson with the OSTP stated on a March 29, 2022 panel:
“Over the past century we have made astonishing gains in public health by focusing on the basics of clean water, food safety, sanitation, and clean outdoor air. But not as much on clean indoor air. Our experience with the COVID-19 pandemic has demonstrated clean indoor air is a vital part of our pandemic preparedness toolkit and our public health toolkit. Taking steps to have cleaner indoor air, which can be achieved by improving ventilation, will not only improve health and wellbeing now, but it is also an investment that will benefit future generations and improve people’s long-term health. I want to be very clear COVID-19 is transmitted through the air. As the CDC has said since May 2021 on their website and the scientific brief on SARS COV 2 transmission, the main way it spreads is through inhalation of air carrying very fine droplets and aerosol that contain infectious virus. Bringing more clean air into a room reduces airborne disease transmission and reduces COVID-19 transmission. For example, having five air changes per hour can reduce transmission risk by 50% or more. Improving indoor air quality does not have to conflict with our goals of energy efficiency. Combined with whole building tune-ups, tuning us the ventilation and air filtration systems needn’t increase energy consumption.”
Think about the statement “indoor air quality does not have to conflict with our goals of energy efficiency”. I agree with this statement as long as we stop doing things the way we have done them for years. Building developers and designers must change the way they think about proper ventilation. Clean indoor air must become the goal and not just acceptable indoor air quality.
It’s time to learn from the past, demonstrated by the below excerpt from Dr. Zeynep Tufekci (Associate Professor at The University of North Carolina at Chapel Hill and writer at The New York Times) who recently gave a brief history of the importance of good IAQ during an OSTP discussion:
“Historically, we’ve always struggled to figure out how diseases spread. We didn’t have the germ theory of disease until the 19th century. Prior, there was a belief that foul air, which was smelly, was the cause of many diseases, forming the miasma theories of disease. We were onto something because poorly ventilated and smelly places are usually polluted places that are more likely to be inhabited by disadvantaged populations. For the rest of the 20th century, scientists accumulated evidence about aerosol transmission but experienced sociological hurdles and were left without assistance or funding. Fast forward to the pandemic, the droplet dogma immediately got repeated as it was happening. However, emerging evidence showed the virus was traveling long distances, it wasn’t transmitting outdoors, and scientists wondered why. Organizations realized something was wrong with the previous logic, and sadly, the evidence wasn’t recognized soon enough. By acknowledging the airborne/aerosol nature of viruses such as COVID-19 and influenza, we get an incredible toolkit that allows us to control many venues and is essential for equity. This is an incredible opportunity to do with indoor air what we did to sanitation and water.”
Dr. Linsey Marr, Professor of Civil and Environmental Engineering at Virginia Tech, added:
“Aerosols float around just like cigarette smoke, they don’t stop at six feet, and they can travel quickly. Even if the air feels still, there’s always some movement carrying these tiny particles around. If the indoor setting is poorly ventilated, those will continue to build up over time. We need to reduce the number of aerosol particles, and we have well-established ways of doing that. The first is ventilation. Move more air through, bringing in virus-free outdoor air and pushing out the stale air that contains all the viral aerosols. This will reduce or dilute the amount of virus in the air.”
Think about the above statements: “emerging evidence showed the virus was traveling long distances, it wasn’t transmitting outdoors” and “aerosols float around just like smoke.” Thinking about being downwind of smoke is a great example of seeing air. The further you are away from the smoker the more diluted the smoke is, however, you can still see it and smell it.
In most cases, you can’t see or smell harmful airborne contaminants, however, we hope that you can now visualize their direction of flow. Considering the virus was traveling long distances indoors, we believe that the energy that created movement was directional airflow. It is time to change the way we think about the dirty off-gassing/return air within buildings.
What we bring into a building also affects the indoor environment. Harmful off-gassing is not only due to human occupants within the building. The furniture, carpets, paints, caulking, glues, etc. also off-gas.
What happens to the alveoli (the tiny air sacs in the lungs) over time when breathing what is currently considered “acceptable air?” Remember the definition of acceptable IAQ “Air in which there are no known contaminants at harmful concentrations.” How do we know what’s in the air if you can’t see it? How do we keep the breathing zone ventilated with good clean air?
In the Test, Adjust and Balance profession, we know the answer because we understand directional airflow. For example, many of the buildings that we work in have minimal return grilles. Notice we called them return grilles, why did we not call them “return air distribution?” I grew up in the South as a NASCAR fan. I can remember hearing fans of Dale Earnhardt say, “Dale can see the air.” I often think about “seeing the air” when thinking about where it comes from and where it is going.
That got me thinking about facilities with cascading pressures between spaces with a focus on the clean (good) air such as cleanrooms and operating rooms. I began thinking about what these facilities have in common that we could implement in our office buildings and classrooms to improve ventilation without increasing the cost of operation. I also thought about the well-documented lack of COVID-19 transmission on commercial airplanes. All three of these indoor spaces focus on four requirements during design: Directional Air Flow, Air Changes, Air Exchanges, and Filtration.
This, I believe, is the answer to the big question “How do we improve the ventilation within the breathing zone without increasing energy cost?” INTENTIONAL DIRECTIONAL AIRFLOW. For years we have been discussing outdoor air volume requirements per square foot or outdoor air per person. We have not adequately addressed the direction of air in a space after it has been exhaled. Consider any indoor space and ask the question, “where is the return grille and how many are installed?”
In most cases, there is one return grille located in the ceiling, near the thermostat. This is a great location for the thermostat to sense the average temperature of the return air. But what about occupants that are inhaling the off-gassing of others in the space? The occupants closest to the return air grille will inhale a higher concentration of airborne particles.
Thus, if we begin to focus on the direction of return air by installing and balancing ceiling supplies with low sidewall returns, we can reduce the outside air volume, thereby reducing energy costs, while still increasing ventilation effectiveness by reducing cross-contamination of the breathing zone common with ceiling returns.
There is minimal upfront cost to low sidewall returns in a classroom or office, however, there are many benefits. Return air distribution is important and we must begin thinking about the direction of the return air. The question that I hear most often is “How do we pay for it?” One way is per ASHRAE standard 62.1-2019 table 6-4 Zone Air Distribution Effectiveness, which shows a decrease in ventilation effectiveness of 0.8 if your air distribution configuration has a “Ceiling supply of warm air 15 degrees F or more above space temperature and ceiling return”.
However, a configuration of “Ceiling supply of warm air and floor return” has a ventilation effectiveness rate of 1.0. Per this standard and these conditions, a low sidewall return distribution system would require 20% less outside air. By having low sidewall returns, the ventilation air will travel once through the breathing zone and not be short-cycled through the ceiling return grille.
How are we going to pay for it? The United States government has made money available per Dr. Alondra Nelson:
“Last year the American rescue plan made available hundreds of billions of dollars for schools, universities, state and local governments, nonprofits, nursing homes, offices, and businesses like restaurants and gyms that can be used to improve indoor air quality. For example, $122 billion were made available through the elementary and secondary school emergency relief fund to help schools prevent the spread of COVID-19, including through ventilation improvements.”
In the end, there is more to consider than just initial cost when building a building. The question to ask is: What is the purpose of a building in the first place? We build buildings to provide safe shelter and comfort. Dr. Joseph Allen (Associate Professor at Harvard T.H. Chan School of Public Health) recently said:
“Many studies have shown higher ventilation rates, higher filtration associated with better reading scores, better math scores for students, and decreases in school absenteeism. The benefits don’t just stop with schools; we see this in offices and workers everywhere. Higher ventilation rates are associated with fewer missed workdays, better cognitive functions, thinking more clearly, less fatigue, and fewer headaches.”
Dr. Joseph Allen’s research on the benefits of ventilation and cognitive function shows that at the cost of $40 per person per year, we see benefits to the business on the order of $6,000-$7,000 per person per year. Massachusetts Institute of Technology (M.I.T.) did a study showing that buildings that are designed and operate to a healthy building standard command effective rents 4%-8% higher per square foot. Healthy buildings are just good business decisions.
Dr. Allen further added, “We’re an indoor species; we spend 90% of our time indoors. It’s intuitive and logical then that the indoor environment has an outsized impact on our health, and we’ve been ignoring it for too long.”
It’s time to rethink why and how we define and design comfort for indoor environments. ASHRAE standard 170-2021 Ventilation of Health Care Facilities Table 7-1 is clear about air changes, air exchanges (outdoor ACH) and filtration, however, ASHRAE standard 62.1-2019 Ventilation for Acceptable Indoor Air Quality does not address ACH or AXH and instead uses a standard of CFM per person. Why is the thought process different for healthcare facilities than it is for commercial buildings? It is time to focus on understanding, designing, and operating unidirectional downward return air distribution systems.
Return air being distributed from a space is vital to preventing contaminated air from re-entering the breathing zone. It’s important to capture the air as close to the source as possible without returning it across the breathing zone. We understand the importance of this concept in cleanrooms, operating rooms, and airplanes. The benefit of adopting similar standards for commercial spaces will far outweigh the cost.
